Born in Lymington, Hampshire, Lyons was the elder son of Edmund Lyons, 1st Baron Lyons (1790–1858), naval officer and diplomat, and his wife, Augusta Louisa, née Rogers (1791–1852). After attending Winchester College, he went to Christ Church, Oxford, where he graduated BA in 1838 and MA in 1843. He entered the diplomatic service in 1839 as an unpaid attaché at his father's legation in Greece. In 1844 he was made a paid attaché and transferred to Saxony and then Tuscany. His first major appointment came in December 1858 when he succeeded Lord Napier as British envoy to the United States in Washington.

Lyons reached Washington a full two years before the American Civil War. Like many observers, he believed that the dissolution of the United States was a strong possibility. Lyons had been seen as the best appointment to the United States by the British government. A capable envoy was an absolute necessity in Anglo-American relations, since both of Lyons' predecessors at Washington (Napier and Crampton) were recalled because of scandals.

Lyons was successful in healing the rift in Anglo-American relations. He moved quickly to resolve the San Juan Island crisis in 1859 (the "Pig War"). Moreover, Lyons planned and oversaw the wildly successful 1860 tour of Canada and the United States by the Prince of Wales. Lyons received high praise on both sides of the Atlantic, from no less than President James Buchanan and Queen Victoria. For these two diplomatic triumphs Lyons was made GCMG.

However, a few weeks after the Prince's tour, the diplomatic and political landscape changed radically. Abraham Lincoln was elected President in November 1860 and the Secession Crisis began. Lyons feared that American politicians might try to divert public opinion from domestic problems by quarreling with foreign powers, especially Britain. He was particularly suspicious of William Henry Seward, Lincoln's Secretary of State.

As the war unfolded, Lyons had to deal with numerous problems. One was the threat to Canada, which he believed could be the target of a possible attack by the Union. Another was the cotton supply to Britain from the Confederacy in spite of the Union blockade of the southern coast.

In 1861, Lyons declared to Lord John Russell that "the taint of slavery will render the cause of the South loathsome to the civilized world."

The most dangerous moment was the Trent affair, which established Lyons' lasting reputation. In the autumn of 1861, the Confederacy sent two envoys (James Mason and John Slidell) to Europe to try to secure formal recognition. They traveled on the (neutral) British mail steamer Trent. A Union warship intercepted the Trent and seized the envoys, outraging British opinion. Public excitement over the affair grew so intense that war between Britain and America seemed for a time unavoidable. Through tact and firmness Lyons was largely responsible for the avoidance of open war between the two countries, persuading the reluctant United States government to release the envoys. The author Raymond A. Jones in his work The British Diplomatic Service, 1815-1914 has stated, unequivocally, that Lyon's handling of the "Mason-Slidell affair... established his well-deserved reputation as Britain's greatest mid-century ambassador." (see p. 126)

In December 1864, Lyons left Washington, citing ill health. Lyons was suffering from what doctors would diagnose today as nervous exhaustion and migraines. Before he left, Lyons had positive final meetings with Lincoln and Seward. Both wished for Lyons' recovery and his return to the U.S. But in the spring of 1865 his poor health forced Lyons to resign his post. The Queen and Prime Minister Palmerston tried their best to get Lyons to return to Washington but to no avail. Instead they appointed Sir Frederick Bruce, who was Lyons' hand-picked successor. This was noteworthy as it showed that the Queen and Palmerston had the utmost confidence in Lyons' ability to read the diplomatic situation.

Queen Victoria remarked to Palmerston that she was so pleased by Lyons' service in the U.S. that she would be happy to have Lyons "represent Her at any Court" in the world. Therefore, a few months later Lyons went to Turkey to replace Sir Henry Bulwer, who was embroiled in a career-destroying scandal. (The Ottoman government had bought him an island estate, and several thousand pounds were missing from the embassy accounts.) The new Foreign Secretary, Lord Clarendon, had full faith and confidence that Lyons would be the "honest man" to clean up the mess and restore positive Anglo-Ottoman relations. Lyons did so in a short amount of time; he stayed in Turkey less than two years.

In October 1867, after the resignation of Lord Cowley, Lyons was moved to Paris, France. He represented Britain in France for a continuous period of twenty years: one of the longest-serving British ambassadors in Paris in modern times. The presence of such a reliable and conciliatory man in the most sensitive and important post in Europe gave both Liberal and Conservative British governments an essential guarantee that their instructions would always be carried out according to the terms determined in London. His efforts on behalf of various governments were rewarded with a viscountcy (1881) and an earldom (1887), though he died before the patent had been sealed on the latter.

The twenty years Lyons spent in Paris were of momentous importance in French history. This period saw the last years of the Second French Empire, its fall and the Franco-Prussian War, the Paris Commune, the establishment of the Third Republic, and the start of the Boulanger crisis. Lord Lyons had decided views on the evolving situation in France. Because he did not consider a working and orderly parliamentary democracy possible in France, he constantly favoured strong men, such as Napoleon III and later the republican leader Léon Gambetta, to lead the country. He believed that only they could pacify France, heal the political and social divisions within French society, and, no less importantly, maintain a strong attachment to the entente with Britain and a commitment to free-trade policy.

These two decades were no less fraught with major international problems: the rise of and the consequences for the European order arising out of the Franco-Prussian War; the Eastern Question; the French invasion of Tunisia and the start of French colonial expansion; and the Egyptian question. On all these issues, Lyons favoured a close understanding between France and Britain, in order to avoid a new confrontation between France and Germany which would, he believed, destroy the entire European system. Following British action in Egypt in the summer of 1882 and the formal end of dual control of that country, Lyons found himself in the midst of a bitter confrontation between Britain and France which lasted until 1904. The last five years of his embassy must rank as the worst time he spent in Paris.

Unlike some in London he accepted the responsibilities facing Britain in Egypt and believed that, having decisively established its authority over Egypt, Britain should not withdraw from the task it had entered upon. He therefore advocated the best possible arrangements both for securing Egypt's finances and for respecting French financial rights there. During this difficult period Lyons contributed greatly, by his conciliatory manner, in preventing the friction between France and Britain from producing any irremediable estrangement.

By the time Lyons relinquished his post at the end of October 1887 he was an exhausted man who, after nearly fifty years of official duties, longed for some rest. On the formation of the second Salisbury administration in 1886, the new prime minister offered him the Foreign Office, but he declined on the grounds of ill health and age. His last days at the embassy were very trying, but in accordance with Salisbury's wish he stayed on a few more months, though not without considerable misgivings. Lord Lytton, who had served under Lyons as chargé d'affaires, succeeded him.

Although it was believed that Lyons had converted to Roman Catholicism, in fact he never did. In 1886, soon after the death of his beloved sister Minna (the dowager Duchess of Norfolk), he received permission from Lord Salisbury to study Catholicism and attend Mass. While Lyons was on the path to conversion, in November 1887 a serious stroke rendered him both paralysed and incapacitated. At the time, Lyons was staying at Norfolk House, St James's Square, London, with his nephew the Duke of Norfolk. Lyons died there on 5 December and was buried beneath the Fitzalan Chapel at Arundel Castle on 10 December. Sadly, Lyons was never able to enjoy the well-deserved rest and the well-deserved retirement he had longed for.

Geoffrey Madan records Lyons as the author of two somewhat surprising aphorisms:

Americans are either wild or dull.

If you're given champagne at lunch, there's a catch somewhere.

Lord Lyons' diplomatic style and his legacy were of paramount importance. He trained many of the British diplomats that held the most important diplomatic posts all over the world for some thirty years after his death. Noteworthy members of the "Lyons School" of diplomacy were Sir Edward Baldwin Malet and Sir Edmund Monson. [See Dr. Scott T. Cairns, "Lord Lyons and Anglo-American Diplomacy During the American Civil War, 1859-1865"; PhD Thesis, The London School of Economics, University of London, 2004.

In Fiction

Lord Lyons appears briefly as a character in the alternative history novel Guns of the South by Harry Turtledove.